Question

My mobile app reads an external json object. How can I check in javascript that a key node exists in the dynamically generated json structure? I tried the hasOwnProperty or containsKey methods, but without luck.

Example json data:

{  "element1": 
  {  "element2": { "Number":  "0" }, 
     "element3": { "Number":  "1" }, 
     "element4": { "Number":  "2" }
  } 
}

As these elements are generated dynamically, I want to check if the key element3 exists in this structure. No luck with data.element1.hasOwnProperty(“element3”).

Answer 1

Yes, hasOwnProperty() method does not work for a Json object. It works for a Java Script Object. So You just need to convert this Json object into a Java Script Object using eval() method and check inside that object.

When you convert above Json structure, it will create an Object (element1) inside another Object (say JSObject). element1 will contain properties element2, element3 and element4. So your code should go like this.

var MyObject={  "element1": 
  {  "element2": { "Number":  "0" }, 
     "element3": { "Number":  "1" }, 
     "element4": { "Number":  "2" }
  } 
}

var JSObject=eval('(' + MyObject+ ')');

var IsExistElement3 = JSObject.element1.hasOwnProperty("element3");